The aims of this research are to: (1) Continue studies on the cataractogenic effects of (a) lysophosphatidyl choline (LPC), a phospholipid which induces cataracts in uveitis; (b) lysophosphatidyl ethanolamine (LPE), a phospholipid which is found in increased levels in senile cataracts and which induces cataracts in rabbits; (c) phospholipids in plasma of patients with senile cataracts and aqueous humor of patients with uveitis. (2) Test inhibitors to LPC and phospholipase A cataracts in the rabbit. (3) Determine the metabolism of cholesterol, sphingomyelin and ceramide in human and animal lenses and in senile cataracts. (4) Determine the lipid composition of lens fiber membranes by preparing right-side-out sealed membranes. Rabbit or human lenses will be cultured in vitro in TC 199-bicarbonate media containing 14C LPC or 14C LPE and the uptake, binding to lens membranes and metabolism determined. In human and animal lenses, the transport and synthesis of cholesterol and incorporation into lens fibers will be determined by incubation in TC 199 media with 14C acetate or 14C cholesterol. Similar studies on the synthesis of sphingomyelin, phosphatidyl ethanolamine, phosphatidyl choline, with H3 choline, P32 and 14C fatty acids will be conducted. Separation of phospholipid subgroups will be accomplished by two-way silica gel thin-layer chromatography. The enzymes lecithin cholesterol acyl transferase, phospholipase A, sphingomyelinase, CDP ceramide phosphotransferase, and ceramidase will be tested for in human lens and senile cataracts. Prior to chemical analysis, clear lenses and senile cataracts will be photographed following the protocol of the National Collaborative Cataract Study. Attempts will be made to obtain resealed right-side-out and inside-out lens membranes similar to those prepared for red blood cells. The information will (a) clarify the cataractogenic effects of LPC and LPE; (b) determine whether lysophospholipids are increased in plasma of patients with senile cataracts or aqueous humor of patients with uveitis; (c) provide basic information on the metabolism and composition of lens fiber membranes in human and animal lenses and in senile cataracts.